1.1 Field of the Invention
The present invention relates to an optical guidance system and more particularly to a seeker system having dual semi-active laser and laser radar modes of operation.
1.2 Description of Related Art
Laser energy is uniquely suited to perform many specialized functions because of its coherent, extremely stable, frequency characteristics, thus making possible the generation and transmission of very well defined and characterized beams of energy. Since the development of practical laser apparatus, such apparatus are finding many applications for locating and identifying remote objects including, in military operations, target marking and guidance systems.
One of the present marking and guidance systems is the semi-active laser (SAL) system. SAL systems have been used by military aircraft to support ground operations. With the SAL system, a narrow laser beam is produced and transmitted toward a target. The laser radiation is typically generated and transmitted from a laser designator aircraft manned by a forward operator. The operator directs the laser radiation to a selected target, thereby designating the target.
The laser radiation reflected from the target can then be detected by the laser seeker head of a missile or other weapon located remote from both the target and the laser energy transmitter. The SAL system includes processing equipment for generating guidance commands to the missile derived from the sensed laser radiation as it is reflected from the target. Such a system can be used by pilots or other users to identify a target and guide the missile or weapon to the target.
Although these systems have proven effective, the next generation missiles are expected to fly to ranges well beyond the range of imaging sensors on board the designator platform. On the other hand, there are many SAL designators already in the field with proven records of extremely high weapon accuracy and positive control.
Another known seeker guidance system is the laser detection and radar (LADAR) system. Unlike its SAL cousin, the LADAR system incorporates its own laser source, thus eliminating the need for an external designator. Typical LADAR systems are adapted to scan a target area with laser energy, detect the reflected radiation, and compute range and intensity values, permitting the processing of guidance and control signals for the weapon as it approaches the target With its specialized data processing capabilities, the LADAR system provides superior ability to acquire targets autonomously.
U.S. Pat. No. 4,085,910 ('910) discloses a dual mode optical seeker device having an infra-red and visible light sensor. The seeker of the '910 functions as a SAL seeker by sensing infra-red radiation transmitted from a designator platform and reflected from a target. The '910 seeker also includes a visible light sensor for determining the orientation of the missile relative to a visible target. Since the '910 seeker requires an external designator and relies on visible light to mark and track a target, it is limited to certain range and environmental conditions. The '910 seeker is also not adapted to rapid scanning possible with LADAR devices.
Advancement in enemy air defense systems drives the need for enhanced weapon guidance capability. It is desirable to further increase the range of modern weapons while still maintaining high accuracy and positive control. Still further, it is desired to implement these capabilities without great alteration or cost to existing weapon systems. Thus, there remains a need for a new, low cost, seeker system that offers advanced capabilities.